stephens999 / fiveMinuteStats

A repo of short "vignettes" illustrating statistical concepts
http://stephens999.github.io/fiveMinuteStats
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Typo in formula for Wright-Fisher Model #67

Open andieich opened 10 months ago

andieich commented 10 months ago

Hi,
I think that there might be a typo in your Introduction to the Wright-Fisher Model (which is very helpful, thanks for that!). If I understood it correctly, your formula:

$$X{t} \mid X{t-1} = x{t-1} \sim Binomial(n = 2N, p = \frac{x{t-1}}{2N})$$

should give the probability for $x_{t}$ and not $x_{t-1}$ and should therefore be:

$$X{t} \mid X{t-1} = x{t} \sim Binomial(n = 2N, p = \frac{x{t-1}}{2N})$$

Is this correct?

stephens999 commented 10 months ago

thanks for the suggestion! The original is correct. The conditioning event is X{t-1}=x{t-1}. Maybe it would help you if I write Xt | (X{t-1}=x_{t-1}) but the extra () are not usually used in this context and make the notation a bit busy.

andieich commented 10 months ago

aaah, now I get it, thanks!